Process for removing deposits from enclosed chambers

ABSTRACT

Alkaline and acid cleaning solutions ( 180, 182 ), are used sequentially for removing organic and inorganic residues, respectively, from the chamber. The two cleaning solutions are stored in separate storage containers ( 52, 54 ) carried by the cart. The alkaline cleaning fluid preferably includes a strong base, such as potassium or sodium hydroxide. The acid cleaning solution includes a strong acid, such as phosphoric acid, which passivates the chamber during the cleaning process. After cleaning is complete, the two cleaning fluids are mixed together to form a neutral or near neutral solution which is disposable in a sanitary sewer system without further treatment.

BACKGROUND OF THE INVENTION

The present invention relates to the chemical cleaning arts. It findsparticular application in conjunction with the removal of baked onresidues from sterilizers, and will be described with particularreference thereto. It should be appreciated, however, that the inventionis also applicable to the cleaning of residues from other processingequipment, such as pharmaceutical, food, and beverage equipment, and thelike.

Steam sterilizers are generally operated at a pressure of about 2 kg/sq.cm (30 psi) and a temperature of around 130° C. Over a period of time,the chamber walls become coated with a residue comprising baked onmaterials, such as boiler compounds, lint, debris, tape and packagingmaterials used to wrap medical devices being sterilized. These residuesinterfere with the efficient operation of the sterilizer or may bedislodged from the chamber walls and soil the sterilized items.

The baked on residues are difficult to remove. Mechanical methods havebeen used to remove the residue, but these are labor intensive. It takesapproximately 6-8 hours to mechanically clean one sterilizer. In onemethod, the chamber walls are blasted with a stream of glass beads. Anair compressor, which is parked outside the facility and connected tothe glass bead equipment by a long air line, powers the equipment. Thechamber is tented to contain the beads and dust generated. A ventilationhood, supplied by a separate air compressor, is worn by the operatingtechnician. The surface of the chamber walls is often left in aroughened condition which is difficult to polish to a smooth finish.

In another method, a hand-held grinding/polishing wheel and an abrasivecompound are used to remove the residue. The grinding wheel is usuallypowered by an air compressor, as for the glass bead method. Thesterilizer is tented to contain dust generated in the process andbreathing equipment is worn by the technician performing the cleaning.In the process, weld joints and studs in the sterilizer may be damagedand additional time is taken to repair the damage. For nickel platedsterilizer chambers, the polishing process may remove the thin nickelplating (typically around 0.5 millimeters in thickness, or less)exposing the underlying carbon steel to subsequent corrosion. Onstainless steel sterilization chambers, damage to weld joints is aproblem.

The present invention provides a new and improved method and cleaningcomposition for cleaning baked-on residue from a vessel which overcomesthe above-referenced problems and others.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a method forcleaning residue from a surface of a sterilizer chamber is provided. Themethod includes contacting the surface with an alkaline cleaningcomposition which consists of between about 10 and 30% of an alkalinecomponent and water. The method further includes separately contactingthe surface with an acid cleaning composition which consists of betweenabout 10 and 55% of an acid component and water. The steps of contactingthe surface with the acid and the alkaline cleaning compositions arecarried out for sufficient time to substantially clean the surface ofresidue.

In accordance with another aspect of the present invention, a two partcomposition for removing baked-on residues from a surface is provided,the residues comprising both organic and inorganic substances. Thecomposition includes a cleaning solution for removing the organicsubstance which includes between about 10 and 30% of an alkalinecomponent, 0.1-5% of a surfactant, 3-20% of a chelating agent, andwater. The composition further includes a cleaning solution for removingthe inorganic substance which includes between about 10 and 55% of anacid component, 0.1-5% of a surfactant, 0.2-10% of a chelating polymer,and water.

One advantage of the present invention is the provision of an easilyportable cleaning system.

Another advantage of the present invention is that a sterilizer iscleaned and ready to be returned to service in about two to four hours.

Yet another advantage of the present invention is that the cleaningcompositions are contained within the system and pose few hazards tooperating technicians.

A further advantage of the present invention is that a neutralizedproduct is formed after cleaning which may be disposed in the normalwaste system.

A yet further advantage of the present invention is that the cleaningcompositions do not have a significant negative influence on the nickelplate on the sterilizer walls.

A still yet further advantage of the present invention is that thesystem is adaptable to a variety of sterilizer shapes and sizes.

Still further advantages of the present invention will become apparentto those of ordinary skill in the art upon reading and understanding thefollowing detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various steps and arrangements of steps. The drawingsare only for purposes of illustrating a preferred embodiment and are notto be construed as limiting the invention.

FIG. 1 is a schematic view of a cleaning system in position on asterilizer, in accordance with a first embodiment of the presentinvention;

FIG. 2 is a side perspective view of the equipment housing of the systemof FIG. 1;

FIG. 3 is a rear perspective view of the equipment housing of FIG. 2with some of the housing panels removed;

FIG. 4 is a front perspective view of the equipment housing of FIG. 2with the housing panels removed;

FIG. 5 is a perspective view of the cleaning system of FIG. 1;

FIG. 6 is a front perspective view of a sterilizer with the lid of thesystem of FIG. 5 positioned for attachment over the opening;

FIG. 7 is a schematic view of an alternative embodiment of part of acleaning system according to the present invention;

FIG. 8 is an alternative embodiment of a cleaning solution supply tankin accordance with the present invention;

FIG. 9 is a schematic view of a part of a cleaning system in position ona sterilizer, in accordance with another embodiment of the presentinvention; and

FIG. 10 is an a schematic view of an alternative cleaning system inposition on a sterilizer, in accordance with another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, a portable system A for cleaningresidues from the interior walls 10 of a sterilizer chamber 12 is shown.The system is particularly suited for cleaning nickel clad sterilizerchamber walls, although it may also be used for cleaning stainless steelsterilizer chambers.

With reference also to FIGS. 3-5, the system A includes a cart 20 fortransporting the system to the sterilizer to be cleaned. The cartincludes a housing 22 with an interior support frame 24 and a base shelf26, a top 28, and four housing panels, namely, an upper front panel 30,a rear panel 32, and two side panels 34 and 36, respectively. The rear,left, and right side panels 32, 34, extend generally vertically betweenthe base and the top and form the rear, and left and right sides of thehousing, respectively. The front panel 30 cooperates with the top, side,and rear panels to form a housing enclosure or upper compartment 38. Thefront panel extends only part way down the front of the cart to provideaccess to a tank storage area or lower compartment 39 below the housingenclosure, as shown in FIG. 2. Two (or more) spaced wheels 40 aremounted to a rear end of the housing adjacent the base 26 formaneuvering the cart around a facility. Additional wheels may bepositioned at the front of the cart for improved stability. A handle 44,mounted to the top of the housing is used for directing the cart.

The housing 22 holds the operating equipment 48 of the system A in theupper compartment 38 and one or more reservoirs or tanks 52,54 ofcleaning fluid in the lower compartment 39. The reservoirs comprisedisposable or refillable containers which are filled with cleaningsolutions. The containers are formed from a relatively rigid material,such as plastic, which is not degraded by the cleaning solutions at thetemperatures used.

With particular reference to FIGS. 1 and 4, the operating equipment 48includes a high pressure pump 60 for pumping a selected cleaningsolution to the chamber 12 of the sterilizer and a scavenge pump 62 forremoving the cleaning solution from the chamber. The operating equipmentalso includes an in-line heater 64, a temperature sensor 66, and,optionally, inlet and outlet strainers or filters 68 and 70,respectively, for filtering particles of dirt from the cleaningsolution. As shown in FIG. 1, the heater 64 includes a heating coil 72,which heats the cleaning solution to a suitable temperature forcleaning, preferably about 55-70° C. at the sterilizer chamber walls,although other methods of heating and heating temperatures are alsocontemplated. The temperature sensor 66 measures the temperature of thecleaning solution just prior to it entering the sterilizer. A controlsystem 74, such as a computer control system or other solid statecontrol system, receives temperature signals from the sensor 66 andregulates the in-line heater 64 accordingly. As shown in FIG. 3, thecontrol system 74 is mounted to the outside of the housing on the rearpanel 32, although other suitable locations are also contemplated.

With particular reference to FIGS. 5 and 6, a demountable lid 80 closesan opening 82 in the sterilizer chamber during cleaning. As best shownin FIG. 6, the lid includes a flat plate 83 which is fixed to an endring 84 of the sterilizer by fixing members, such as clamping bolts 86.The end ring is typically formed from monel and is not exposed to theconditions within the sterilizer chamber 12 during sterilization. Thus,it remains relatively free from tarnish or deposits. The bolts includeblocks 88, which are fixed to an outer surface 90 of the lid plate 83.The blocks are spaced from the outer edge of the lid plate. Swivelheaded screws 92, tapped through the blocks and lid plate, turn threadedfeet 94 mounted to the screws on the inside of the lid plate until theyengage the inside surface of the end ring 84 of the sterilizer toposition the lid.

A suction-tight fit between the end ring 84 and the lid 80 is providedby the scavenger pump 62. Specifically, during cleaning, the scavengerpump is set to create a sub-atmospheric pressure within the sterilizerchamber (i.e., a slight negative pressure), thus sealing the lid 80against the end ring 84. This provides containment of the cleaningsolutions and their vapors. To achieve the pressure differential, thescavenger pump 62 pumps the cleaning solution out of the chamber 12 at ahigher rate than the high pressure pump 60 pumps it in. Optionally, asealing member 98, such as a gasket, is fitted between the end ring andthe lid. Preferably, the gasket is glued, or otherwise attached to aninside surface 100 of the lid plate around the perimeter thereof. An airbleed line 104, with a valve 106, is connected with the lid plate 83 forreleasing the pressure inside the chamber 12 once cleaning is completeto facilitate removal of the lid.

The lid plate 83 is sized according to the size of the chamber opening82. Commercial sterilizers often have openings of 16″×16″ (about 40cm×40 cm), 20″×20″ (about 50 cm×50 cm), or 24″×36″ (about 60 cm×90 cm).Accordingly, it is desirable to provide several, interchangeable lids 80of different plate sizes for servicing different size chambers.Preferred lid plates are formed from plastic or stainless steel and havea thickness of about 0.3-1.0 cm. The lids are stored on the cart 20 whennot in use. As shown in FIGS. 2 and 5, a storage bin 108 is mounted forthis purpose on the side panel 36 of the cart, although it is alsocontemplated that the bin could also be accommodated on the rear orfront panels of the housing 22.

With reference once more to FIGS. 1, 5, and 6, a first, or inlet fluidline 120 carries the cleaning solution from a selected one of thecleaning solution reservoirs 52, 54 via the high pressure pump 60, theheater 64, and the temperature sensor 66, to the lid 80. The heaterpreferably heats the fluid to a temperature suitable for cleaning thesterilizer, generally above about 18° C. The inlet fluid line passesthrough a first, centrally positioned opening 122 in the lid plate 83 toa nozzle 124 releasably mounted to the chamber side 100 of the lidplate. When not in use, the nozzle 124 is stored in the storage bin 108,as shown in FIG. 5.

With particular reference to FIGS. 2 and 5, a disconnectable portion 128of the first fluid line 120 between the housing 22 and the lid 80 ispreferably formed from a length of flexible hose with quick connectorcouplings 130A, 132A at first and second ends, respectively, for quicklyconnecting with corresponding quick connector couplings 130B and 132B,on the front panel 30 of the housing and on the lid 80, respectively.When not in use, the hose 128 is uncoupled from the lid and the housingquick connectors 132B, 130B and stored on a hose reel 134 mounted on oneof the side panels 34 of the housing, as shown in FIG. 2.

A first three way valve 136, such as a directional ball valve, in thefluid inlet line 120 is fluidly connected between the two cleaningsolution reservoirs 52, 54 and the high pressure pump 60 for selectivelydelivering cleaning solution from one of the cleaning solutionreservoirs 52, 54 to the chamber 12. Optionally, a manually operatedvalve 140 in the fluid inlet line 120 allows the inlet line to beclosed, in case of accidental leakage of fluid, such as from thesterilizer chamber.

With particular reference to FIG. 5, the nozzle 124 sprays the cleaningsolution over the walls 10 of the sterilizer chamber. A preferred nozzleis one which systematically sprays the entire surface of the chamberwalls such that an even coverage of the cleaning solution is obtained.The nozzle may have one or more spray heads 142. A particularlypreferred nozzle includes an articulating spray head 142, which isarticulated for rotation about two perpendicular axes C, D (i.e., itrotates in three axes). The articulation is powered by the pressure ofthe cleaning solution entering the nozzle 124, such that over a periodof a few minutes, the spray head 142 makes a series of rotational passeswhich provide complete coverage of the chamber walls 10. The nozzleincludes a rigid tubular portion 144 which releasably connects the sprayhead with the interior surface 100 of the lid plate by quick connect132B, or other convenient means. The tubular portion 144 is of asuitable length for positioning the spray head 142 at or near the centerof the sterilizer chamber 12. Spray heads with different length tubularportions 144 may be stored in the cart storage bin 108 for accommodatingsterilizers of different lengths.

The high pressure pump 60 preferably supplies the cleaning solution tothe nozzle 124 at a high pressure (around 2 Kg/sq. cm). This providesthe spray with mechanical cleaning action which assists in removing theresidue from the chamber walls. The spray head preferably deliverscleaning solution at a pressure of 3.5-85 Kg/cm², or greater, and at aflow rate of 25-160 liters per minute, or greater.

With reference once more to FIGS. 1 and 5, a second, return fluid line150 connects the sterilizer chamber 12 with the reservoirs 52,54 via asecond, lower opening 152 in the lid plate 83, the outlet strainer 70,and scavenger pump 62, in sequence. While FIG. 1 shows the heater 64 inthe inlet line, it is also contemplated that the heater may bepositioned in the return line 150, or elsewhere in the system.

The sterilizer includes a drain fitting 164, which is positioned at thelowest point of the sterilizer chamber. The cleaning solution sprayedfrom the nozzle 124 drips off the walls 10 of the chamber and runs downto the drain fitting. A scavenge fitting 166, at the chamber end of thesecond fluid line 150 is releasably connected with the drain fitting.The scavenge pump 62 sucks the collected solution from the chamber drainfitting, along the return fluid line and through the filter 70, wherelarge particles of dirt and other debris are removed, which couldotherwise cause damage to the pumps or block the nozzle. The returningsolution is then heated by the in-line heater 64. A second three wayvalve 168, such as a directional ball valve, in the return fluid line150 directs the heated cleaning solution to a selected one of thereservoirs 52,54.

As for the inlet line 120, a portion 170 of the return line 150 betweenthe lid 80 and the housing is formed from a length of flexible hosewhich includes quick connect couplings 172A, 174A at first and secondends for quickly connecting with corresponding couplings 172B, 174B onthe front panel of the housing and lid 80 respectively. Optionally, thehose reel 134 on the side panel of the housing is also used for storingthe hose 170 between use.

An analysis of the residues found on sterilizer walls, by varioustechniques, such as X-ray Photoelectron Spectroscopy (XPS), has shownthat both organic and inorganic substances are present in the residue.To facilitate removal of both types of residue, a two step cleaningprocess is preferably used. In a first step, an alkaline cleaningsolution, which is used to remove organic materials, is sprayed over thechamber walls. In a second step, an acid cleaning solution, which isformulated for removing inorganic materials, is sprayed over the chamberwalls 10. The order of the two step process may be reversed, with theacid cleaning step followed by the alkaline cleaning step. However, itis preferable to remove the organic residues first. The two cleaningsolutions may be prepared by diluting concentrated cleaning compositionswith water or supplied in the dilute form, ready for use.

The first reservoir 52 contains the alkaline cleaning solution 180 andthe second reservoir 54 contains the acid cleaning solution 182. Thecleaning solutions are withdrawn from the reservoirs through first andsecond inlet line conduits 184 and 186, which releasably connect thecleaning solution reservoirs 52, 54, respectively, with the first ballvalve 136. The inlet line conduits are fluidly connected with siphontubes 188, 190 inside each of the reservoirs, which extend upward fromthe lower ends of the reservoirs 52, 54, respectively. Optionally, eachsiphon tube 188, 190 includes an integral filter 192, 194, respectively,adjacent its lower end, for filtering cleaning solution leaving thereservoir. Optionally, the filter replaces the strainer 68 in the inletline 120. The first three way valve 136 is switched so as to connectfirst the alkaline fluid inlet line conduit 184 and, subsequently, theacid fluid inlet line conduit 186 with the high pressure pump 60.Similarly, the cleaning fluid is returned to the reservoirs throughfirst and second return conduits 198 and 200. The second three way valve168 connects the scavenger pump 62 with the first and second returnconduits 198, 200 in turn, to return the alkaline cleaning composition180 to the alkaline reservoir 52 and subsequently, the acid cleaningcomposition 182 to the acid reservoir 54. Quick connectors on theconduits 184, 186, 198, 200 connect with corresponding quick connectorson the reservoirs 52, 54 for rapid connection and disconnection of thefluid inlet and outlet lines from the reservoirs.

The reservoirs 52, 54 are of a suitable size for containing sufficientcleaning solution to fill the hoses and conduits during cleaning. Formost purposes, a 2-8 gallon tank is a convenient size for each of thereservoirs.

Optionally, as shown in FIG. 7 a third reservoir 204 contains a rinsefluid 206, such as tap wayter, or distilled water, for removing thecleaning composition from the chamber and from the various hoses, pumps,and conduits, at the end of the cleaning process. Conduits 208 and 210connect the rinse fluid reservoir 170 with the inlet and return lines120, 170 via three way valves 212 and 214, respectively. When the threeway valves 212, 214 are in a position to direct rinse fluid to and fromthe chamber, the three way valves 136, 168 are preferably switched to aclosed position such that no cleaning solution passes from thereservoirs 52, 54 to the chamber 12.

Alternatively, the rinse inlet conduit 208 is connected with a mainssupply of tap water for rinsing the chamber after cleaning. The rinsereturn conduit 210 is optionally connected with a drain or suitablypositioned receptacle. In yet another alternative embodiment, the returnvalves 168 and 214 are switched to return the used rinse water from thechamber to one of the cleaning fluid reservoirs.

Operation of the various pumps and valves is preferably controlled bythe control system 74, which is mounted in the upper housingcompartment. The pumps are optionally switched on and off manually, byswitches 218 on a control panel 220 conveniently mounted on the outsideof the control system. FIG. 2 shows the control panel 220 mounted on therear housing panel 32, although other convenient locations are alsocontemplated. Optionally, additional switches 224, shown in FIG. 2 on aside panel, manually operate the ball valves 136, 168, 212, 214. Morepreferably, the control system 74 operates the switching of the ballvalves so that the sterilizer is first cleaned with the alkaline cleaner180 for a first, preselected time then cleaned with the acid cleaner 182for a second, preselected time, and finally, rinsed with the rinse fluid206.

With reference once more to FIG. 2, the operating equipment ispreferably powered by electricity, which is supplied through anelectrical cord 230 connected to the mains supply of the facility.Alternatively, the equipment may be powered by a battery or a generatormounted on the cart.

The acid and alkaline cleaning solutions 180, 182 are preferably mixedtogether when cleaning is complete to form a neutral, or near neutralsolution which is safe to dispose of in a sanitary sewer system, withoutfurther treatment. By near neutral, it is meant that the cleaningsolutions, when combined, have a pH of 6 to 8, more preferably, a pH of6.5 to 7.5. Accordingly, the volumes, and or the pH of the two cleaningsolutions used are preferably selected such that, when mixed, a nearneutral solution is formed.

In one embodiment, shown in FIG. 7, a connecting portion or wall 200,which forms a barrier between the first and second reservoirs 52,54, isopened after cleaning to allow the two cleaning solutions to mix. Themixing results in the formation of a neutral, or near neutralcomposition. Various opening mechanisms are contemplated. In onepreferred embodiment, an opening member, such as a cutter 202 cuts theconnecting wall between the two reservoirs to allow mixing. The openingmember is preferably actuated by an actuator 204, such as a solenoidvalve, which is operated by the control system 74. In anotherembodiment, a valve (not shown) is opened to allow cleaning solution topass between the two reservoirs.

In another alternative embodiment, the alkaline reservoir 52 is sized toaccommodate both the acid and the alkaline cleaning solutions 180, 182.At the end of the acid cleaning portion of the cleaning cycle, thereturn ball valve 168 is switched so that the acid cleaning solution 182is directed into the alkaline reservoir 52. The high pressure pump andscavenger pumps 60, 62 continue to pump the acid cleaning solution fromthe acid reservoir 54 until all the acid cleaning solution has passedthrough the chamber 12 and into the alkaline reservoir, where it mixeswith the alkaline cleaning solution. This method of circulation can alsobe used to enhance mixing when a barrier 200 between the two reservoirsis opened, as described above.

In operation, fresh reservoirs 52,54 of cleaning solution are loadedinto the lower compartment 39 of the cart 20 and the quick connectors onthe conduits 186, 184, 198, 200 connected with the correspondingconnectors on the reservoirs. The cart is then wheeled through thefacility and positioned adjacent to the sterilizer to be cleaned. Theelectric cord 230 is connected to a suitable mains outlet. A suitablysized lid 80 and nozzle attachment 124 are selected and connectedtogether by quick connect fitting 133B. A door 232 to the sterilizer isopened and the lid 80 clamped to the end ring 84 of the chamber to sealthe opening 82, as shown in FIG. 6. Quick connections 174, 172 are madebetween the return hose 170 and the drain fitting 166 and the housing22, respectively. Similarly, quick connections 132, 130 are made toconnect the inlet hose 128 with the nozzle 124 and the housing,respectively. The pumps 60, 62 are switched on and the heater 64 beginsto heat the alkaline cleaning solution to the desired temperature forcleaning. Heating is continued while the alkaline cleaning solution iscirculated through the chamber until the desired cleaning temperature isreached. Heating is continued, as needed, to maintain the temperature.

The three way valves 136,168 are set by the controller 74, or setmanually, so that the alkaline cleaning solution 180 is pumped along thefluid inlet line 120 to the nozzle 124 by the high pressure pump 60 andthe sprayed cleaning solution is returned to the same tank 52 along thefluid return line 150 by the scavenger pump 62.

The scavenger pump 62 operates to maintain a slight negative pressure inthe chamber. This assists in keeping the lid 80 in a sealing relationwith the end ring 84 and ensures that the sprayed cleaning solution isremoved quickly from the bottom of the chamber. The bottom of thechamber is the area of the chamber where the cleaning solution andresidue tends to accumulate. It is, therefore, desirable to prevent thecleaning solution from pooling there and inhibiting the mechanicalcleaning action of the spray. Residues which are carried from thechamber into the tank 52 are filtered from the recirculating cleaningsolution by the return strainer 70 so that they do not clog the nozzlespray head 142 and other parts of the equipment.

After a period of cleaning, typically 1-2 hours for heavily encrustedresidue, or less for lightly soiled chambers, the high pressure pump 60is switched off temporarily while the first (alkaline) cleaning solution180 remaining in the chamber and fluid lines is returned to the firsttank 52. The three way valves 136,168 are then switched so that thesecond cleaning solution (acid) 182 is circulated through the chamber inthe same manner as described above for the alkaline cleaning solution180. This is continued for a period sufficient to remove remaining,inorganic residue from the chamber, typically 1-2 hours for heavilysoiled chambers, or less for lightly soiled chambers. Since the cleaningsolutions do not significantly influence the nickel plating on thechamber walls, the cleaning process may be further extended to ensurethorough cleaning.

The chamber walls are cleaned and passivated in the cleaning process.Passivation is the reduction in the tendency of a metal to corrode.Passivity may result from the formation of a thin semiconducting oxidefilm on the metal surface (termed chemical passivity) or theprecipitation of solid salts to form a thicker, but porous layer (termedmechanical passivity). Oxidizing agents, such as phosphoric acid, arecapable of passivating iron and steel chambers.

During the cleaning of the chamber interior 12, the chamber door 232, incases where it is not cleaned by the process, may be cleaned byconventional cleaning methods, such as hand cleaning. Alternatively, areplaceable cover for the interior of the door is conveniently replacedat this time.

At the end of the cleaning process, the connecting portion 200 betweenthe two tanks 52,54 is opened and the cleaning solutions allowed to mix,and/or other mixing methods, as described above, are employed.Optionally, the mixed cleaning solution is circulated through thechamber 12 and fluid lines 120, 150 to neutralize remaining cleaningsolutions thereon.

Alternatively, or additionally, a rinse cycle is used to wash thechamber and hoses. Rinse fluid 206 is pumped by the high pressure pump60 through the inlet fluid line 120 to the nozzle 124 and returned bythe scavenger pump 62 to one of the cleaning solution tanks, the rinsetank 204, or to a drain or other receptacle. In this way, the hoses canbe handled safely without risk of drops of cleaning solution falling onthe technician or outside the chamber. The quick connectors on the twotanks 52, 54 are then disconnected from the corresponding conduits andthe tanks emptied into the sanitary sewer system, or transported to adisposal facility.

The air bleed valve 106 is opened to allow air to enter through the airline 104 into the sterilizer chamber to equalize the pressure inside thechamber. The lid 80 is then unclamped from the sterilizer end ring 84.The lid 80, nozzle 124, and hoses 128,170 are uncoupled and stored onthe cart 20.

The entire cleaning process is readily completed in 2-4 hours, muchfaster than for conventional cleaning methods. Additionally, since thesolid state control 74 controls many or all of the operations of thecleaning process, the technician is free to perform other servicingfunctions during the cleaning time.

If desired, the acid and alkaline cleaning steps may be repeated one ormore times, for example, if the sterilizer chamber is heavily encrustedwith deposits. Fresh cleaning solutions may be used for each repeatedcleaning step. Or, the same solutions may be reused.

In yet another embodiment, shown in FIG. 8, a single reservoir 310replaces the two cleaning solution reservoirs 52, 54 and includes afirst chamber 312 which receives a cleaning solution suitable forremoving all types of deposits from the sterilizer. Such a system isused, for example, when the deposits from the sterilizer are easier toremove, or are relatively less heavily accreted, or is used atintervals, in between major two-reservoir cleaning processes, to keepdeposit buildup to an acceptable level. In this embodiment, aneutralizing chamber 314 is separately formed in the reservoir forreceiving a neutralizing agent. The neutralizing agent is a chemicalwhich reacts with the cleaning solution to form a non-hazardoussubstance which may be disposed in the sanitary sewer system, orotherwise safely disposed. For example, if the cleaning solution isacidic, the neutralizing agent is alkaline, and vice versa.

After cleaning is complete, an actuator 316 causes an opening member318, such as a cutter, to pierce a connecting wall 320 between theneutralizing chamber and the cleaning solution chamber. The neutralizingagent mixes with the used cleaning solution to form a neutral solution.The actuator 316 may be a solenoid valve, operated by a control system,as described above, or a manual actuator, as shown in FIG. 8. A simpleactuator, which is disposable along with the reservoir, includes acompressible tube 324, formed from paper, plastic, or the like whichhouses an upper end of the cutter. The tube 324 inhibits accidentalactuation of the cutter prior to and during cleaning. A lower end of thecutter, which defines a cutting edge or blade 323 or other suitablecutting shape, is positioned in the neutralizing chamber (or,alternatively, in the cleaning solution chamber), adjacent theconnecting wall 320. An operator presses an upper end of the tube 324,crushing the tube and depressing the cutter 318 until the cutting edge323 cuts the connecting wall 320.

A siphon tube 332 includes an integral filter 334 for filtering cleaningsolution leaving the reservoir. Optionally, the filter replaces thestrainer in the inlet line. The syphon tube is connected with an inletline quick connector 336 for quickly connecting the syphon tube with theinlet line. A return quick connector 338 couples a return line with thecleaning solution chamber 312. The operating equipment and cart used inthis embodiment are essentially as shown in FIGS. 1 and 2. However, theball valves 136 and 168 are preferably eliminated in this embodiment orreplaced with simple open and shut type valves.

With reference to FIG. 9, an embodiment of the system suitable for usein sterilizers having a door 400 with a generally centrally positionedopening 402, passing through the door, is shown. This embodiment takesadvantage of the readily available central opening to supply cleaningfluid to the chamber. Certain sterilizers, particularly larger models ofthe radial arm type, have a closure mechanism (not shown) which makesuse of the central opening. In such cases, parts of the closuremechanism are readily removable. For example, in the case of an Amscobrand 24×36 radial arm sterilizer, the door diaphragm cover, diaphragm,and clutch rod assembly are first removed from the inside 404 of thedoor. On the outside 406 of the door, the door handwheel and clutch lockcap are then removed, thereby providing an opening 402 with access tothe sterilizer chamber 408 from the outside of the sterilizer. Parts ofthe door mechanism 409, which do not obstruct the opening, are left inposition on the door. This embodiment allows the inside of the door tobe cleaned at the same time as the chamber walls, without the need forseparate, hand cleaning.

Once the appropriate parts of the closure mechanism have been removed,an adapter 410, is fitted to the inside (or to the outside) of the door.The adapter has an attachment portion 412, which is suitably shaped forinterconnection with the door around the opening, for example by meansof a screw thread, clamp, or other method of attachment. A horizontallyextending bore 414 is defined through the adapter with an internaldiameter sufficient to receive an inlet tube 416 therethrough. The inlettube thus passes through the opening 402 in the door and into thechamber interior. The inlet tube is conveniently formed from a length of⅜″ stainless steel or rigid plastic pipe, or other rigid material whichis resistant to the cleaning fluids used. A seal 418, such as an O-ring,provides a leak-tight seal between the tube and the bore. The seal maybe held in place by a nut 420 threaded into one end of the inlet tube.Other methods of sealing the inlet tube to the adaptor are alsocontemplated, including welding of the inlet tube to the adapter bore414.

A nozzle 422 is attached to an inner end 424 of the tube 416 forspraying cleaning fluid over the walls of the chamber and the innersurface of the door. The length of the inlet tube is selected so as toposition the nozzle so that the cleaning fluid reaches all the walls ofthe chamber and the inner surface of the door during the cleaningprocess.

An outer end 426 of the inlet tube is connected with the cleaning fluidsupply reservoirs 52, 54, in a similar manner to that shown in FIG. 1.For example, the outer end may include a quick connect coupling 428which couples with a corresponding quick connect coupling at the end ofthe flexible hose 128 (shown in FIG. 1). Alternatively, the inlet tubemay be connected with a single reservoir of the type illustrated in FIG.8.

An outlet line 430, for withdrawing the sprayed cleaning fluid from thechamber, may be connected to a lower end of the chamber through a secondopening in the sterilizer chamber 408. The outlet line 430 is connectedto a separate outlet 432 at a lower end of the sterilizer, by quickconnects 434, or other suitable connectors, as shown in FIG. 9.

FIG. 10 shows an alternative embodiment of the system, in which thein-line heater 64 is omitted. In this embodiment, the cleaning solutionis heated in the sterilizer by employing the sterilizer's own heatingsystem 450. For example, the sterilizer of FIG. 1 is surrounded by asteam jacket 450. The steam jacket is supplied with steam through avalve 452 while the cleaning solution is circulated through the chamber12. When a sensor 466 displays that the cleaning solution is at theselected temperature for effective cleaning, the steam supply to thesteam jacket 450 is switched off by closing the valve. If the sensorsubsequently registers that the temperature of the cleaning solution isbelow an acceptable level, the steam supply may be recommenced.

In this embodiment, it is preferable for the temperature sensor 466 tobe positioned in the return line 170, where it measures the temperatureof the cleaning solution just after it leaves the chamber 12. Thecontrol system 60, in this embodiment, does not control the addition ofsteam to the sterilizer, although it is also contemplated that thesterilizer may be modified so that the control system controls theopening of the steam valve 452 automatically, in response to detectedsolution temperatures received from the sensor 466.

Cleaning Compositions

The acidic cleaning solution 182 includes an acid component andpreferably also includes a surfactant, a chelating polymer, and thebalance water.

The acid component is preferably a strong acid, having a low pH(preferably about pH 0-3, more preferably, 0-2 for a 0.1M aqueoussolution of the acid). Suitable acid components include phosphoric acid,hydroxyacetic acid (glycolic acid), and sulfamic acid. Phosphoric acid,which has a passivating effect on stainless steel, is particularlypreferred. The acid component is preferably present at the concentrationof about 14-55%, more preferably, present at a concentration of about40-50% weight, most preferably at about 45-48% by weight of the acidiccleaning solution. The acid component can be a combination of two ormore acids.

For example, a cleaner containing about 42% phosphoric acid (readilyformed by using 60% of a 70% W/W phosphoric acid solution) and about 5%by weight citric acid is particularly effective.

The surfactant is selected from the group consisting of anionic,cationic, nonionic, and zwitterionic surfactants to enhance cleaningperformance. Examples of such surfactants include water soluble salts ofhigher fatty acid monoglyceride monosulfates, such as the sodium salt ofthe monosulfated monoglyceride of hydrogenated coconut oil fatty acids,higher alkyl sulfates, such as sodium lauryl sulfate, alkyl arylsulfonates, such as sodium dodecyl benzene sulfonate, higher alkylsulfoacetates, higher fatty acid esters of 1,2 dihydroxypropanesulfonates, and the substantially saturated higher aliphatic acyl amidesof lower aliphatic amino carboxylic acid compounds, such as those having12-16 carbons in the fatty acid, alkyl, or acyl radicals, and the like.Examples of the last mentioned amides are N-lauroyl, N-miristoyl, orN-palmitoyl sarcosines.

Additional examples are condensation products of ethylene oxide withvarious reactive hydrogen compounds reactive therewith having longhydrophobic chains (e.g. aliphatic chains of about 12-20 carbon atoms),which condensation products (“ethoxamers”) contain hydrophilicpolyethylene moieties, such as condensation products of poly(ethyleneoxide) with fatty acids, fatty alcohols, fatty amides, polyhydricalcohols (e.g. sorbitan monostearate), and polypropyleneoxide (e.g.pluronic materials).

Particularly preferred surfactants are low foaming amphotericsurfactants or anionic surfactants (generally not low foaming), eitheralone, or in combination with non-ionic surfactants. Miranol JEM, anamphocarboxylate, short chain, low foaming surfactant obtainable fromRhone-Poulenc as a 45% by weight solution is a typical suitablesurfactant. The surfactant is present in the cleaning solution at aconcentration of about 0.1-5.0% by weight, more preferably, around0.2-3.0%, most preferably, at about 0.3% by weight.

The polymer is preferably one which is stable in the acid conditions.Suitable polymers include acrylamides, polyacrylates, and otherchelating polymers, alone or in combination. One suitable polymer is TRC233i, an acrylamide-type polymer obtainable from Calgon Corporation. Thepolymer is preferably at a concentration of 0.2-10% by weight, morepreferably, around 0.2-2.0%, most preferably, at around 1% by weight ofthe acid cleaning solution.

Water suitable for the present invention can be distilled water, softwater, or hard water. Soft water is preferred.

A preferred acid cleaning solution includes, in terms of weight percent.

Component Weight % Preferred weight % Phosphoric acid 14-55  45-48Citric Acid 0-10 2-8 Surfactant 0.1-5   0.2-3   Polymer 0-10 0.2-2  Water Q.S.

The alkaline cleaning solution 180 includes an alkaline component andpreferably also a surfactant, a chelating agent, and the balance water.

The alkaline component is preferably a strong base, having a high pH(preferably, pH 13-14 for a 0.1M solution of the base), such as sodiumhydroxide or potassium hydroxide, or a combination thereof. Othersuitable alkaline components include quaternary ammonium hydroxides,such as alkyl quaternary ammonium hydroxides, including tetramethylammonium hydroxide, tetraethyl ammonium hydroxide, and the like. Thealkaline component is preferably present at a concentration of 10-30%,more preferably, at around 20-25% by weight. A particularly preferredalkaline cleaning composition includes 21.0% potassium hydroxide(readily prepared by using 47% by weight of 45% W/W potassium hydroxidesolution).

The surfactant is preferably as described for the acid cleaningsolution. A preferred alkaline cleaning solution includes Miranol JEM.The surfactant is preferably at a concentration of 0.4-5%, and morepreferably, about 0.9% by weight of the alkaline cleaning solution. Forexample, a 0.9% concentration can be achieved using 2% Miranol JEM(since this is a 45% solution).

The chelator is present at a concentration of from about 3-20% of thealkaline cleaning composition 180. It preferably includes a polyacrylicacid, at a concentration of 0.1 to 3% by weight, more preferably, ataround 0.3% by weight of the alkaline cleaning composition. The chelatormay also include sodium gluconate at a concentration of 1-7%, morepreferably, at around 4-5%, most preferably, at around 5% by weight ofthe alkaline cleaning solution. The chelator may also include EDTA or asalt thereof at a concentration of 2-6%, more preferably at around 2-4%,most preferably, at about 4% of the alkaline cleaning composition.

Optionally, the alkaline cleaning composition 180 may include more thanone alkaline component, more than one surfactant, and more than onechelating agent.

A preferred alkaline cleaning solution 180 includes, in terms of weightpercent.

Component Weight % Preferred weight % Potassium hydroxide 10-30 20-25Sodium Gluconate 0-7 4-5 Sodium EDTA 0-6 2-4 Surfactant 0.4-5   about0.9 Polyacrylic acid 0.1 to 3 about 0.3 Soft Water Q.S.

The two step cleaning system (one acid, one alkaline) thus describedcleans and passivates the sterilizer chamber. Alternatively, one orother of the alkaline and acid cleaning solutions may be used in thesingle reservoir 310 of FIG. 8.

The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents hereof.

Having thus described the preferred embodiment, the invention is nowclaimed to be:
 1. A method for cleaning residue from a surface of asterilizer chamber, the method comprising: spraying with a pressure ofat least 3.5 Kg/cm² the surface with an alkaline cleaning compositionwhich consists of: a) between about 10 and 30% of an alkaline component,b) water, and, optionally, surfactant and chelating agent; and,separately, spraying the surface with an acid cleaning composition whichconsists of: a) between about 10 and 55% of phosphoric acid, and b)water, and, optionally, surfactant and chelating agent; the steps ofspraying the surface with the acid and the alkaline cleaningcompositions being carried out for sufficient time to substantiallyclean the surface; after the steps of spraying, combining the sprayedacid cleaning composition with the sprayed alkaline cleaning compositionto form a combined solution for disposal; and rinsing the surface with aneutral pH or near neutral pH solution having a pH of from 6-8 formed bycombining the acid cleaning composition and the alkaline cleaningcomposition to neutralize the surface.
 2. The method of claim 1, whereinat least one of the alkaline cleaning composition and the acid cleaningcomposition further includes between 0.1 and 5% of a surfactant.
 3. Themethod of claim 1, wherein the alkaline component further includesbetween 3 and 20% of a chelating agent.
 4. The method of claim 3,wherein the chelating agent is selected form the group consisting ofpolyacrylic acid, sodium gluconate, ethylenediamine tetraacetic acid,salts of ethylenediamine tetraacetic acid, and combinations thereof. 5.The method of claim 1, wherein the acid cleaning composition furtherincludes 0.2 and 10% of a chelating polymer.
 6. The method of claim 1,wherein the alkaline component consists essentially of a base selectedfrom the group consisting of potassium hydroxide, sodium hydroxide,quaternary ammonium hydroxides, and combinations thereof.
 7. The methodof claim 6, wherein the hydroxide is at a concentration of 20-25% byweight.
 8. The method of claim 1, wherein the acid cleaning compositionfurther includes an acid selected from the group consisting ofhydroxyacetic acid, sulfamic acid, and combinations thereof.
 9. Themethod of claim 1, wherein the phosphoric acid is at a concentration ofabout 40-50%, by weight.
 10. The method of claim 1, wherein the alkalinecleaning step is carried out before the acid cleaning step.
 11. Themethod of claim 1, wherein: the sterilizer chamber surface is stainlesssteel or nickel plated; in the alkaline cleaning step, the alkalinecleaning solution is continuously circulated over the surface untilorganic soils are dissolved and removed; and in the acid cleaning step,the acid cleaning composition includes phosphoric acid, and the acidcleaning composition is continuously circulated over the surfaceconcurrently dissolving and removing inorganic soils and passivating thesterilizer chamber surface.
 12. The method of claim 1, wherein: thealkaline cleaning composition further includes: 0.1 to 5 weight % of asurfactant; 3 to 20 weight % of a chelating agent; and the acid cleaningcomposition further includes: 0.1 to 5 weight % of a surfactant, and 0.2to 10 weight % of a chelating polymer.
 13. A method for cleaning residuefrom a stainless steel surface of a sterilizer chamber and safelydisposing used cleaning fluids, the method comprising: (a) recirculatingan alkaline cleaning fluid from a first chamber to the stainless steelsurface and back to remove organic residue; (b) after removing organicresidue, returning the alkaline cleaning fluid to the first chamber; (c)recirculating an acid cleaning fluid from a second chamber to thesurface and back to remove any remaining inorganic residue and topassivate the organic residue-free stainless steel surface; (d) afterpassivating the stainless steel surface, returning the acid cleaningfluid to the second chamber; (e) after steps (a) through (d),neutralizing the alkaline and acid cleaning fluids by mixing all of thealkaline cleaning fluid with the acid cleaning fluid to form a mixtureof neutral or near neutral pH in at least one of the first and secondchambers; (f) circulating the near neutral pH mixture of the alkalineand acid cleaning fluids through the sterilizer chamber; and (g)disposing of the neutralized mixture.
 14. The method of claim 13,wherein the step of mixing includes: forming an opening in a connectingwall between the first and second chambers.
 15. The method of claim 13,wherein the step of mixing includes: opening a valve in a fluid linewhich connects the first and second chambers.
 16. A method for cleaninglayers of baked-on organic and inorganic residue from a surface of asteam sterilizer chamber which layers have been subject to numerouscycles of steam heating at over 100° C. and cooling to room temperature,the surface being formed from the stainless steel or nickel plate, themethod comprising: (a) providing a spray nozzle inside the sterilizerchamber pumping alkaline cleaning composition from one compartment tothe spray nozzle inside the sterilizer chamber, the alkaline cleaningcomposition including one of the group consisting of sodium hydroxide,potassium hydroxide, and combinations thereof; (b) spraying the alkalinecleaning composition from the spray nozzle onto the surface of thesterilizer chamber to attack organic residue, the spraying being with asufficiently high force to provide a mechanical cleaning action; (c)pumping an acid cleaning composition from another compartment to thespray nozzle inside the sterilizer chamber separately from the alkalinecleaning composition, the acid cleaning composition including phosphoricacid; and (d) spraying the acid cleaning composition from the spraynozzle separately from the alkaline cleaning composition onto thesurface of the sterilizer to attack the inorganic residue, the sprayingbeing with a sufficiently high force to provide a mechanical cleaningaction; steps (b) and (d) being carried out for sufficient time tosubstantially clean and passivate the stainless steel or nickel platesurface.
 17. A method for removing organic and inorganic residue, lint,organic materials, tape and packaging materials that have accumulatedand been repeatedly baked-on a stainless steel interior surface of asteam sterilizer at temperatures over 100° C., over numerous thermalsterilization cycles, the method comprising: providing a spray nozzleinside the sterilizer chamber; spraying a phosphoric acid cleaningcomposition from the spray nozzle onto the stainless steel interiorsurface of the steam sterilizer with a pressure that provides mechanicalcleaning along with chemical cleaning to attack the baked-on residue;spraying an alkaline cleaning composition, comprising sodium hydroxide,potassium hydroxide and combination thereof, from the spray nozzle ontothe stainless steel interior surface of the steam sterilizer with thepressure that provides a mechanical cleaning action along with chemicalcleaning to attack the baked-on residue; carrying out the spraying stepsin either order for a duration sufficient to substantially clean thebaked-on residue and passivate the stainless steel interior surface. 18.The method of claim 17, wherein each spraying step is carried out for1-2 hours.
 19. The method of claim 17, wherein the spraying is conductedat a pressure of 3.5-85 kg/cm² and with a flow rate of 25-160liters/minute.
 20. The method of claim 17, wherein the steps ofseparately spraying the alkaline cleaning composition and the acidcleaning composition are repeated.
 21. A method for removing a build-upof organic and inorganic residue from a nickel-plated interior surfaceof a steam sterilizer chamber, which residue has been repeatedlybaked-on to the nickel surface over numerous thermal steam sterilizationcycles, the method comprising: providing a spray nozzle inside thesterilizer chamber; separately spraying an acid cleaning composition andalkaline cleaning composition from a spray nozzle onto the nickelsurface of the steam sterilizer chamber with sufficient pressure thatthe spray provides a mechanical cleaning action which assists inremoving the baked-on residue layers, the alkaline cleaning compositionattacking at least the organic residue layers and the acid compositionattacking at least the inorganic residue.
 22. The method of claim 21,wherein the alkaline cleaning composition includes at least one of:sodium hydroxide, potassium hydroxide, and combinations thereof.
 23. Themethod of claim 22, wherein the acid cleaning composition includesphosphoric acid.
 24. The method of claim 22, wherein the step ofspraying the alkaline cleaning composition is carried out for at leastan hour, and the step of spraying the acid cleaning composition iscarried out for at least an hour.